CN113991080A - Positive electrode material and preparation method and application thereof - Google Patents
Positive electrode material and preparation method and application thereof Download PDFInfo
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- 239000007774 positive electrode material Substances 0.000 title claims abstract description 30
- 238000002360 preparation method Methods 0.000 title abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 58
- 238000002156 mixing Methods 0.000 claims abstract description 21
- 239000000725 suspension Substances 0.000 claims abstract description 18
- 239000011247 coating layer Substances 0.000 claims abstract description 8
- 238000003756 stirring Methods 0.000 claims description 23
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 18
- 229910001416 lithium ion Inorganic materials 0.000 claims description 18
- 238000005245 sintering Methods 0.000 claims description 17
- 229910052493 LiFePO4 Inorganic materials 0.000 claims description 14
- 239000010406 cathode material Substances 0.000 claims description 14
- 238000005406 washing Methods 0.000 claims description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 9
- 229910010710 LiFePO Inorganic materials 0.000 claims description 9
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 8
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 8
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 7
- 238000001914 filtration Methods 0.000 claims description 6
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 239000002904 solvent Substances 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 6
- 239000006185 dispersion Substances 0.000 claims 2
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 abstract description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 22
- 229910052799 carbon Inorganic materials 0.000 abstract description 21
- 239000011248 coating agent Substances 0.000 abstract description 11
- 238000000576 coating method Methods 0.000 abstract description 11
- 229910010707 LiFePO 4 Inorganic materials 0.000 abstract description 3
- 229910039444 MoC Inorganic materials 0.000 description 24
- 102100028667 C-type lectin domain family 4 member A Human genes 0.000 description 19
- 101000766908 Homo sapiens C-type lectin domain family 4 member A Proteins 0.000 description 19
- 230000000052 comparative effect Effects 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 239000002243 precursor Substances 0.000 description 6
- 239000010405 anode material Substances 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 5
- 229910021641 deionized water Inorganic materials 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 238000000967 suction filtration Methods 0.000 description 5
- 239000000843 powder Substances 0.000 description 4
- 238000004804 winding Methods 0.000 description 4
- QIJNJJZPYXGIQM-UHFFFAOYSA-N 1lambda4,2lambda4-dimolybdacyclopropa-1,2,3-triene Chemical compound [Mo]=C=[Mo] QIJNJJZPYXGIQM-UHFFFAOYSA-N 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 239000002033 PVDF binder Substances 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 239000003292 glue Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 238000011031 large-scale manufacturing process Methods 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 229910013872 LiPF Inorganic materials 0.000 description 2
- 101150058243 Lipf gene Proteins 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000006257 cathode slurry Substances 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 238000007765 extrusion coating Methods 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000003746 solid phase reaction Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- QCDWFXQBSFUVSP-UHFFFAOYSA-N 2-phenoxyethanol Chemical compound OCCOC1=CC=CC=C1 QCDWFXQBSFUVSP-UHFFFAOYSA-N 0.000 description 1
- NONFLFDSOSZQHR-UHFFFAOYSA-N 3-(trimethylsilyl)propionic acid Chemical compound C[Si](C)(C)CCC(O)=O NONFLFDSOSZQHR-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 229910012258 LiPO Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- YWEUIGNSBFLMFL-UHFFFAOYSA-N diphosphonate Chemical compound O=P(=O)OP(=O)=O YWEUIGNSBFLMFL-UHFFFAOYSA-N 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229960005323 phenoxyethanol Drugs 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- DLYUQMMRRRQYAE-UHFFFAOYSA-N phosphorus pentoxide Inorganic materials O1P(O2)(=O)OP3(=O)OP1(=O)OP2(=O)O3 DLYUQMMRRRQYAE-UHFFFAOYSA-N 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Composite Materials (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
本发明提供了一种正极材料及其制备方法和用途。所述正极材料包括内核和包覆于所述内核表面的MoC包覆层，所述内核包括LiFePO4材料。所述制备方法包括以下步骤：(1)将MoC与LiFePO4材料进行分散混合，得到混合悬浊液；(2)将步骤(1)所述混合悬浊液进行分离，得到分离物，然后烧结，得到所述正极材料。本发明通过采用MoC来包覆磷酸铁锂材料，相对于常规的碳包覆，材料的导电性更佳，并且还有效地降低了阻抗，提升了电池的电化学性能。The present invention provides a positive electrode material and a preparation method and application thereof. The positive electrode material includes an inner core and a MoC coating layer coated on the surface of the inner core, and the inner core includes a LiFePO 4 material. The preparation method includes the following steps: (1) dispersing and mixing MoC and LiFePO 4 materials to obtain a mixed suspension; (2) separating the mixed suspension in step (1) to obtain a separated product, which is then sintered , to obtain the positive electrode material. In the present invention, MoC is used to coat the lithium iron phosphate material. Compared with the conventional carbon coating, the material has better conductivity, and also effectively reduces the impedance and improves the electrochemical performance of the battery.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, relates to a positive electrode material, a preparation method and application thereof, and particularly relates to a lithium iron phosphate positive electrode material, a preparation method and application thereof.
Background
Lithium Ion Batteries (LIBs) have become an integral part of our daily lives, and their shadows are seen everywhere from portable electronic devices such as mobile phones and computers to electric vehicles, and even power stations. The higher energy density of other secondary battery systems is one of the major reasons why LIBs are currently gaining favor. The LIB body we see today is, in fact, the result of a consistent effort in the direction of electrode material-based solid state chemistry by researchers over the last half century. The discovery of new materials and deepening of the basic understanding of the mutual relationship of the structure, the components, the properties and the performance of the new materials play an important role in promoting the development of the LIB field. However, we should also clearly recognize that, currently among many LIB components, the positive electrode is just one of the major "drivers" that limit further increases in energy density and dominate battery cost.
Among them, lithium iron phosphate (LiFePO)4) The theoretical capacity of the anode material is 170mAh/g, the reversible charge-discharge specific capacity is higher, and the anode material has the advantages of wide raw material source, low pollution, good safety, long cycle life and the like, and is an ideal anode material for power-type and energy-storage lithium ion batteries at present. However, due to the limitation of the self structure, the ionic conductivity and the electronic conductivity of the lithium iron phosphate are both low, and the lithium iron phosphate is only suitable for charging and discharging under a low current density, and the specific capacity is reduced during high-rate charging and discharging, so that the application of the material is limited.
CN102332583A discloses a method for preparing a surface carbon-coated lithium iron phosphate positive electrode material for a lithium battery, in which a prepared carbon fluid material is fully mixed with a precursor material for preparing lithium iron phosphate by a solid-phase reaction, and the good coating performance of the carbon fluid material on the precursor material is utilized to finally generate the lithium iron phosphate positive electrode material for the lithium battery with a good carbon coating layer by the solid-phase reaction. However, the preparation method adopted in the document is very complex, and the liquid organic carbon source all uses water as a medium, many micropores in the lithium iron phosphate material cause a capillary phenomenon due to the surface tension of water, and the carbon source cannot enter the micropores, so that the coating area of the organic carbon source is greatly reduced.
CN101494288A discloses a preparation method of lithium iron phosphate as a positive electrode material of a lithium ion secondary battery, which comprises the following steps: A. mixing a lithium source compound, a ferrous source compound, a phosphorus source compound and an organic micromolecular carbon source additive, ball-milling and sintering to obtain a sintering precursor; B. and C, mixing the sintering precursor in the step A with an organic high molecular polymer carbon source additive, ball-milling, sintering and crushing to obtain finished lithium iron phosphate powder. However, this solution has a limited ability to improve conductivity and is cumbersome to handle.
Therefore, how to effectively improve the conductivity of the lithium iron phosphate cathode material is a technical problem to be solved urgently.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a positive electrode material and a preparation method and application thereof. According to the invention, the MoC is adopted to coat the lithium iron phosphate material, so that compared with the conventional carbon coating, the material has better conductivity, the impedance is effectively reduced, and the electrochemical performance of the battery is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a positive electrode material, which comprises an inner core and a MoC coating layer coated on the surface of the inner core, wherein the inner core comprises LiFePO4A material.
According to the invention, the MoC is adopted to coat the lithium iron phosphate material, so that compared with the conventional carbon coating, the material has better conductivity, the impedance is effectively reduced, and the electrochemical performance of the battery is improved.
In a second aspect, the present invention provides a method for preparing the positive electrode material according to the first aspect, the method comprising the steps of:
(1) mixing MoC with LiFePO4Dispersing and mixing the materials to obtain a mixed suspension;
(2) and (2) separating the mixed suspension liquid obtained in the step (1) to obtain a separated substance, and then sintering to obtain the cathode material.
The preparation method provided by the invention can enable the molybdenum carbide to be tightly coated on the surface of the lithium iron phosphate anode material, and the MoC is adopted to coat the lithium iron phosphate material, so that compared with the conventional carbon coating, the material has better conductivity, the impedance is effectively reduced, the electrochemical performance of the battery is improved, the preparation method is simple to operate, excessive and complicated steps are not needed, and the preparation method is suitable for large-scale production.
Preferably, the MoC and the LiFePO in the step (1)4The mass ratio of the materials is (0.05-0.2): 1, such as 0.05:1, 0.08:1, 0.1:1, 0.12:1, 0.15:1, 0.18:1 or 0.2: 1.
In the invention, MoC and LiFePO4The mass ratio of the material is too small, which is not beneficial to improving the conductivity of the material; and if the mass ratio is too large, the resistance to lithium ion migration increases.
Preferably, the solvent for dispersive mixing includes absolute ethanol and or acetone.
Preferably, the dispersing and mixing assistant is polyvinylpyrrolidone.
In the invention, the dispersing aid is beneficial to MoC and LiFePO4The material is better dispersed.
Preferably, the method of dispersive mixing is stirring.
Preferably, the rotation speed of the stirring is 800-1500 r/min, such as 800r/min, 900r/min, 1000r/min, 1100r/min, 1200r/min, 1300r/min, 1400r/min or 1500 r/min.
Preferably, the stirring time is 1-5 h, such as 1h, 2h, 3h, 4h or 5 h.
Preferably, the separation method in step (2) comprises filtration washing and/or centrifugal washing.
Preferably, the number of filtration washes is ≧ 3, such as 3, 4, 5, or 6, etc.
Preferably, the isolate of step (2) is dried.
Preferably, the sintering temperature in the step (2) is 350-500 ℃, for example 350 ℃, 400 ℃, 450 ℃ or 500 ℃.
In the invention, the excessive sintering temperature can cause the breakage of the material particles and reduce the performance, and if the excessive sintering temperature is too low, the material particles with complete appearance are not easy to form.
Preferably, the sintering time in the step (2) is 5-8 h, such as 5h, 6h, 7h or 8 h.
As a preferred technical scheme, the preparation method comprises the following steps:
(1) MoC and LiFePO with the mass ratio of (0.05-0.2): 14Adding the material and the dispersing aid into a solvent, and stirring at the rotating speed of 800-1500 r/min for 1-5 hours to obtain a mixed suspension;
(2) and (2) filtering and washing the mixed suspension obtained in the step (1) for at least three times to obtain a separated substance, drying, and sintering at 350-500 ℃ for 5-8 h to obtain the cathode material.
In a third aspect, the present invention further provides a lithium ion battery, which is characterized in that the lithium ion battery includes the positive electrode material according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, MoC is adopted to coat the lithium iron phosphate material, compared with conventional carbon coating, the material has better conductivity, the impedance is effectively reduced, the electrochemical performance of the battery is improved, and the preparation method is simple to operate and is suitable for large-scale production.
(2) The battery provided by the invention has the advantages that the DCIR (discharge resistance) at low temperature (-20 ℃) is obviously reduced, for example, the DCIR is reduced to below 3.3432m omega when SOC (90%), the DCIR is reduced to below 3.3330m omega when SOC (50%), the DCIR is reduced to below 3.3321m omega when SOC (30%) is realized, the DCIR (discharge resistance) at normal temperature (25 ℃) is also obviously reduced, for example, the DCIR is reduced to below 3.3325m omega when SOC (90%), the DCIR is reduced to below 3.3312m omega when SOC (50%) is realized, and the DCIR is reduced to below 3.3324m omega when SOC (30%) is realized.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a positive electrode material, which includes an inner core and a MoC coating layer coated on the surface of the inner core, where the inner core is LiFePO4A material.
The preparation method of the cathode material comprises the following steps:
(1) mixing LiFePO4The material was placed in a beaker and then the MoC powder (MoC and LiFePO) was weighed4The mass ratio of the materials is 0.05:1), placing the materials into a beaker, adding absolute ethyl alcohol, simultaneously adding 0.05 percent of polyvinylpyrrolidone (PVP) which accounts for 0.05 percent of the total mass of the solution as a dispersing aid, and stirring the mixture for 2 hours at the speed of 1000r/min to obtain mixed suspension;
(2) and (3) carrying out suction filtration on the obtained suspension in a suction filtration machine, washing with absolute ethyl alcohol and deionized water, repeating for three times, then placing the suspension in an oven at 80 ℃ overnight for drying, and sintering at 400 ℃ for 6 hours to obtain the cathode material.
Example 2
The embodiment provides a positive electrode material, which includes an inner core and a MoC coating layer coated on the surface of the inner core, where the inner core is LiFePO4A material.
The preparation method of the cathode material comprises the following steps:
(1) mixing LiFePO4The material was placed in a beaker and then the MoC powder (MoC and LiFePO) was weighed4The mass ratio of the materials is 0.1:1), placing the materials into a beaker, adding absolute ethyl alcohol, simultaneously adding 0.05 percent of polyvinylpyrrolidone (PVP) which accounts for 0.05 percent of the total mass of the solution as a dispersing aid, and stirring the mixture for 5 hours at the speed of 800r/min to obtain mixed suspension;
(2) and (3) carrying out suction filtration on the obtained suspension in a suction filtration machine, washing with absolute ethyl alcohol and deionized water, repeating for three times, then placing the suspension in an oven at 80 ℃ overnight for drying, and sintering at 500 ℃ for 5 hours to obtain the cathode material.
Example 3
This embodiment provides a positive electrode material that is,the anode material comprises an inner core and a MoC coating layer coated on the surface of the inner core, wherein the inner core is LiFePO4A material.
The preparation method of the cathode material comprises the following steps:
(1) mixing LiFePO4The material was placed in a beaker and then the MoC powder (MoC and LiFePO) was weighed4The mass ratio of the materials is 0.2:1), placing the materials into a beaker, adding absolute ethyl alcohol, simultaneously adding 0.05 percent of polyvinylpyrrolidone (PVP) which accounts for 0.05 percent of the total mass of the solution as a dispersing aid, and stirring the mixture for 1h at the speed of 1500r/min to obtain mixed suspension;
(2) and (3) carrying out suction filtration on the obtained suspension in a suction filter, washing with absolute ethyl alcohol and deionized water, repeating for five times, then placing the suspension in an oven at 80 ℃ for overnight drying, and sintering at 350 ℃ for 8 hours to obtain the cathode material.
Example 4
The difference between this embodiment and embodiment 1 is that in this embodiment, MoC and LiFePO4The mass ratio of the materials was 0.3: 1.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 1
The comparative example provides a lithium iron phosphate cathode material, which is LiFePO in example 14A material. (purchased from German Nano)
Comparative example 2
The comparative example provides a positive electrode material, which comprises an inner core and a carbon coating layer coated on the surface of the inner core, wherein the inner core is LiFePO4A material.
The preparation method of the cathode material comprises the following steps:
respectively selecting lithium carbonate, iron oxide and phosphorus pentoxide according to a molar ratio of Li to Fe to P of 1.2 to 1, adding and mixing phenoxyethanol according to a proportion that a carbon source material is selected from 200g per mol of the iron source material, then adding absolute ethyl alcohol to wet-grind for 5 hours, taking out and evaporating to obtain a precursor, then placing the precursor in a heating furnace, adding nitrogen-hydrogen mixed gas, heating to 800 ℃, preserving heat for 10 hours, and cooling to room temperature to obtain the carbon-coated lithium iron phosphate.
(a) The positive electrode materials provided by examples 1-4 and comparative examples 1-2 are used as positive active materials to prepare a positive electrode piece, and the preparation process is as follows:
1) mixing NMP and PVDF in a stirring kettle at normal temperature to prepare positive glue solution with 6% solid content for later use;
2) stirring the positive electrode materials and SP provided by the examples 1-4 and the comparative examples 1-2 for 60min in a stirring kettle according to the mass ratio of 95.5: 1.8;
3) adding a certain amount of NMP into the stirring kettle, and stirring for 2 hours;
4) to the above slurry was added a certain amount of CNT and PVDF gum solution, where LiFePO 4: CNT: the mass ratio of PVDF is 95.5: 1:1.7, stirring for 3 hours to prepare anode slurry with the solid content of 55 percent;
5) uniformly coating the positive electrode slurry on a carbon-coated aluminum foil of 10um by adopting extrusion coating, and drying at 120 ℃ to obtain a dry positive electrode plate, wherein the single-side surface density of the positive electrode plate is 90g/m2；
(b) The preparation process of the lithium ion battery negative plate comprises the following steps:
1) uniformly mixing CMC and deionized water in a stirring kettle at normal temperature to prepare a negative pole glue solution with the solid content of 1.5 percent for later use;
2) mixing graphite and SP in a mass ratio of 96:1.8 in another stirring kettle, and stirring for 60 min;
3) adding CMC glue solution and aqueous binder (polyvinyl alcohol) into the stirring kettle in the step 1), and stirring for 120min, wherein the mass ratio of the CMC to the aqueous binder is 0.4: 1.8;
4) adding a certain amount of deionized water into the cathode slurry, and stirring for 120min to finally prepare cathode slurry with the solid content of 47%;
5) uniformly coating the negative electrode slurry on a carbon-coated copper foil with the thickness of 4.5um by adopting extrusion coating, and drying at 90 ℃ to prepare a dry negative electrode plate, wherein the single-side surface density of the plate is 49g/m2；
(c) Preparation of lithium ion battery electrolyte
The electrolyte was prepared in an argon-filled glove box, in which the hands were keptThe water content in the jacket is less than 10ppm and the oxygen content is less than 1 ppm. The preparation of the electrolyte comprises the following steps: the ratio by volume of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) was 30: 40: 30 LiPF with 1.2mol/L configuration6And LFSI (LiPF)6: LFSI ═ 0.9:0.3) electrolyte, then 0.3 wt.% additive VC, 1.5 wt.% FEC, 0.5% DTD, 0.3% TMSP and 0.5% LiPO were added2F2And mixing uniformly for later use.
(d) Assembly of lithium ion batteries
Winding the positive plate, the diaphragm and the negative plate provided in the embodiments 1 to 4 and the comparative examples 1 to 2 to form a winding core, welding tabs on two sides of the battery core, placing the winding core in an aluminum shell, welding a cover plate, baking the winding core in a baking oven at 100 ℃ for 24 hours, injecting the electrolyte into the aluminum shell, standing at high temperature, forming, performing secondary injection, standing and grading to obtain the corresponding lithium ion battery. The diaphragm is a polyethylene diaphragm with the thickness of 12um, the thickness of the lithium ion battery is 18mm, the width of the lithium ion battery is 150mm, the height of the lithium ion battery is 120mm, and the rated capacity of the lithium ion battery is 22Ah (1C-22A).
The cells provided in examples 1 to 4 and comparative examples 1 to 2 were subjected to DCIR tests, and the cells were subjected to discharge DCIR tests of 90% SOC, 50% SOC and 30% SOC, using 1C, 30s as test conditions, and DCIR at both temperatures of 25 ℃ and-20 ℃, and the data results are shown in table 1.
TABLE 1
From the data results of example 1 and example 4, it is understood that the mass ratio of molybdenum carbide is too large, and the lithium ion transfer distance increases, and the impedance of the material itself increases.
As is clear from the data results of example 1 and comparative example 1, it was found that the uncoated material had a higher resistance and affected the conductivity of the material itself without any coating of the lithium iron phosphate material.
As can be seen from the data results of example 1 and comparative example 2, the molybdenum carbide-coated lithium iron phosphate material of the present invention has lower impedance and better conductivity than the conventional carbon-coated lithium iron phosphate material.
In conclusion, the MoC is adopted to coat the lithium iron phosphate material, so that compared with the conventional carbon coating, the material has better conductivity, the impedance is effectively reduced, the electrochemical performance of the battery is improved, and the preparation method is simple to operate and is suitable for large-scale production. The battery provided by the invention has the advantages that the DCIR (discharge resistance) at low temperature (-20 ℃) is obviously reduced, for example, the DCIR is reduced to below 3.3432m omega when SOC (90%), the DCIR is reduced to below 3.3330m omega when SOC (50%), the DCIR is reduced to below 3.3321m omega when SOC (30%) is realized, the DCIR (discharge resistance) at normal temperature (25 ℃) is also obviously reduced, for example, the DCIR is reduced to below 3.3325m omega when SOC (90%), the DCIR is reduced to below 3.3312m omega when SOC (50%) is realized, and the DCIR is reduced to below 3.3324m omega when SOC (30%) is realized.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The cathode material is characterized by comprising an inner core and a MoC coating layer coated on the surface of the inner core, wherein the inner core comprises LiFePO4A material.
2. A method for producing a positive electrode material according to claim 1, comprising the steps of:
(1) mixing MoC with LiFePO4Dispersing and mixing the materials to obtain a mixed suspensionTurbid liquid;
(2) and (2) separating the mixed suspension liquid obtained in the step (1) to obtain a separated substance, and then sintering to obtain the cathode material.
3. The method for preparing a positive electrode material according to claim 2, wherein the MoC and LiFePO of step (1) are mixed together4The mass ratio of the materials is (0.05-0.2): 1.
4. The method for producing a positive electrode material according to claim 2 or 3, wherein the solvent for dispersion mixing includes absolute ethyl alcohol and/or acetone;
preferably, the dispersing and mixing assistant is polyvinylpyrrolidone.
5. The method for producing a positive electrode material according to any one of claims 2 to 4, wherein the method of dispersion mixing is stirring;
preferably, the rotating speed of the stirring is 800-1500 r/min;
preferably, the stirring time is 1-5 h.
6. The method for producing a positive electrode material according to any one of claims 2 to 5, wherein the separation method of step (2) comprises filtration washing and/or centrifugal washing;
preferably, the number of filtration washing times is more than or equal to 3.
7. The method for producing a positive electrode material according to any one of claims 2 to 6, wherein the isolate of step (2) is dried.
8. The method for preparing a positive electrode material according to any one of claims 2 to 7, wherein the sintering temperature in the step (2) is 350 to 500 ℃;
preferably, the sintering time in the step (2) is 5-8 h.
9. The method for producing a positive electrode material according to any one of claims 2 to 8, characterized by comprising the steps of:
(1) MoC and LiFePO with the mass ratio of (0.05-0.2): 14Adding the material and the dispersing aid into a solvent, and stirring at the rotating speed of 800-1500 r/min for 1-5 hours to obtain a mixed suspension;
(2) and (2) filtering and washing the mixed suspension obtained in the step (1) for at least three times to obtain a separated substance, drying, and sintering at 350-500 ℃ for 5-8 h to obtain the cathode material.
10. A lithium ion battery, characterized in that the lithium ion battery comprises the positive electrode material according to claim 1.
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